The invention relates to a method of folding a gas bag for a vehicle occupant restraint system, as well as to a folded gas bag for a vehicle occupant restraint system.
Numerous methods are known of translating a gas bag for vehicle occupant restraint system from an unfolded condition into a compact folded condition, in which the gas bag can be accommodated in a housing. In one known method fold tongues are used which are placed on the gas bag and form folding edges along which the gas bag can be folded together. Another known method uses pushers with which the gas bag is pushed together. The drawback of all these methods is the expense in being implemented.
The object of the invention consists in providing a method of folding a gas bag which can be implemented cost-effectively.
According to the invention, a method of folding a gas bag comprises the following steps: firstly, the gas bag is unfolded between a base and an opposing surface, with a spacing being provided between the base and the opposing surface, this spacing corresponding to the height of a housing into which the gas bag is to be inserted after folding. Then, a folding funnel is provided which comprises one end having a large cross-section and one end having a small cross-section, the large cross-section being larger than or equal to a cross-section of the gas bag when unfolded between the base and the opposing surface, and the small cross-section corresponding to a cross-section of the housing. Finally, beginning with its large cross-section, the folding funnel is placed over the unfolded gas bag and moved relative thereto such that the gas bag is pushed together on the base by the folding funnel to the small cross-section. This folding method is thus based on pushing the gas bag together from the outside to the inside. Contrary to the pushers as known from prior art which are shifted in the same direction in which the gas bag is pushed together, the component, i.e. the folding funnel of the method according to the invention is slipped, so-to-speak, past the gas bag; the direction of movement of the folding funnel is roughly perpendicular to the direction in which the wall of the gas bag is pushed together. Due to the special cross-sectional shape of the folding funnel the wall of the gas bag is thereby pushed together from outside to the inside. The special advantage of this method lies in the fact that the gas bag is folded by a linear motion of one component only, namely the folding funnel. Such a motion is very easy to automate. Another advantage of the method according to the invention lies in the fact that practically any contour of the folded gas bag pack can be achieved by the corresponding shape of the small cross-section of the folding funnel at no extra expense whatsoever. When, for example, the housing for accommodating the gas bag has an oval cross-section, the folding funnel is configured with an oval small cross-section. In this way the gas bag is pushed together into a pack likewise having an oval cross-section.
A gas bag according to the invention that can be folded by the method according to the invention comprises a wall with a multitude of chaotically oriented single folds and an upper, substantially flat outer side and a lower, substantially flat outer side, with more single folds being provided in one of the outer sides than in the respective other outer side. This arrangement of single folds results from the relative movement between the folding funnel and the wall of the gas bag; corresponding to the direction of movement of the folding funnel the wall is shifted more strongly to the front outer side of the gas bag, as seen in the direction of movement of the folding funnel, so that the wall in this location becomes pleated.
Advantageous aspects of the invention will be apparent from the sub-claims.